66688889021 has 2 divisors, whose sum is σ = 66688889022. Its totient is φ = 66688889020.

The previous prime is 66688888997. The next prime is 66688889041. The reversal of 66688889021 is 12098888666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 45296608900 + 21392280121 = 212830^2 + 146261^2 .

It is a cyclic number.

It is not a de Polignac number, because 66688889021 - 2²⁶ = 66621780157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66688889041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33344444510 + 33344444511.

It is an arithmetic number, because the mean of its divisors is an integer number (33344444511).

Almost surely, 2^66688889021 is an apocalyptic number.

It is an amenable number.

66688889021 is a deficient number, since it is larger than the sum of its proper divisors (1).

66688889021 is an equidigital number, since it uses as much as digits as its factorization.

66688889021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15925248, while the sum is 62.

The spelling of 66688889021 in words is "sixty-six billion, six hundred eighty-eight million, eight hundred eighty-nine thousand, twenty-one".